The ability of a substance to enter the gas phase under given conditions. In perfumery, it helps explain the variability of compositions over time. The evaporation rate also depends on the temperature, substrate and other ingredients of the mixture.
From liquid to air
For a substance to be sensed, its molecules must reach the olfactory system. Volatility describes the tendency to enter the gas phase and depends, among other things, on the temperature and surroundings of the material in the mixture. The scent does not evaporate like several completely independent layers. The carrier and other ingredients change the release conditions. The material that is quickly noticeable after application does not have to be the same one that has the greatest impact on the final impression after a few hours.
Longevity, projection and volatility answer other questions. The material may remain on the skin but be hardly noticeable from a distance. It may also clearly dominate at the beginning and then give way to the background. You should not rank the quality of perfumes solely by the speed at which the first impression appears.
Meaning and application
The smell immediately after spraying and the smell after a long time may differ significantly. Individual materials have different properties, and the reception depends on the entire composition. The first fresh impression does not have to describe what will dominate later.
In practice
When comparing, write down two or three moments of judgment rather than one immediate reaction. Use the products separately and without adding a new fragrance to the tested area. Note which stage suits you best and whether the subsequent background suits the occasion.
Volatility should not be converted into a simple table of hours for each note. It also does not specify the expiry date of the bottle. If the smell, appearance or packaging is questionable, check storage conditions and manufacturer information instead of explaining every change with a pyramid.